The present invention relates to a vane type rotary machine suitable for use as a compressor, pump or the like.
Vane type rotary machines are well known and find various uses such as compressors, pumps and so forth. Generally, a van type rotary machine includes a cylinder having an inner peripheral contour represented by an epitrochoid-like curve having n (n being a natural member) lobes, and a cylindrical rotor which contacts the inner peripheral surface of the cylinder at n points. The rotor is provided with a plurality of radial vane grooves which are communicated with one another at their bottoms. The vane grooves slidably receives vanes the ends of which are pressed against the inner peripheral surface of the cylinder. For example, as shown in FIG. 1, a vane-type rotary machine having three lobes includes a cylinder rotor 3 having an inner peripheral contour of an eptirochoid-like curve, with the cylindrical rotor 3 having vane grooves 2 for slidably accommodating vanes 4 which make resilient sliding contact with the inner peripheral surface of the cylinder 1. When this vane-type rotary machine operates as a vane-type compressor, the vanes reciprocate within the respective vane grooves 2 while sliding on an inner peripheral surface of the cylinder 1 in accordance with the rotation of the rotor 3, so that the volume of each space 5 defined by adjacent vanes 4, rotor 3 and cylinder 1 is periodically changed to thereby effect the compression.
In the rotary machine of the aforementioned type, the compression chamber is divided into sections at portions where a distance between the rotor 3 and the inner peripheral surface 1 is minimized; therefore, it is essential to preserve a good seal at such portions. An effective measure to preserve a good seal at this portion is to insure that such portions of the inner peripheral surface of the cylinder 1 have the form of a circle concentric with the cylindrical surface of the rotor over a substantial circumferential width and to form a surface seal between the cylinder 1 and the rotor 3 at each of such portions.
More particularly, as shown in FIG. 2, the inner peripheral contour assumes a continuous basic curve l contacting a circle of a given diameter at one or more points and an arc m having a radius slightly greater than the radius of the circle, with the curve l and the arc m being connected through suitable transient curves R or, alternatively, connected by common tangential lines as shown in FIG. 3.
However, since the inner peripheral contour has discontinuous portions such as transient curves R (FIG. 2) or the common tangential lines (FIG. 3), the vanes 4 sliding on the inner peripheral surface of the cylinder 1 are made to move irregularly when they pass such discontinuous portion. The irregular motion of the vanes 4 causes chattering of the vanes resulting in local wear of the vanes 4, generation of noise and other troubles.
In, for example, co-pending United States application corresponding to Japanese patent application No. 125,226/1981, a rotary machine, usable as a compressor, pump, or the like, is disclosed which includes a cylinder having an inner peripheral contour formed by a epitrochoidal curve having one or more lobes, a cylindrical rotor having a plurality of vane grooves and contacting the inner peripheral surface of the cylinder, and vanes slidably received by the respective vane grooves. The inner peripheral contour of the cylinder is modified such that the portion of the maximum expansion thereof is offset in a direction of rotation of the rotor to thereby suppress the lateral reactional force applied to the vanes to diminish the friction loss attributable to the sliding of the vanes while, at the same time, obtaining a motion of each vane approximating a sine-wave curve so as to avoid any noise, thermal loss and mechanical damage attributable to irregular motion of the vanes.